Scroll compressors having a fixed scroll and a movable scroll, and forming a compression chamber by engaging wraps of the respective scrolls have been known. In such a scroll compressor, the movable scroll rotates eccentrically with respect to the fixed scroll, thereby sucking a low-temperature, low-pressure fluid into the compression chamber from a portion closer to the outer circumferences of the wraps, and discharging a high-temperature, high-pressure fluid, which has been compressed in the compression chamber, from a discharge port that is open at a central portion of the wraps (see, e.g., Japanese Unexamined Patent Publication No. H7-189937).
Japanese Unexamined Patent Publication No. H7-189937 discloses that in such a scroll compressor, a ratio (i.e., a compression ratio) between a pressure at the start of the intake and a pressure at the completion of the compression is uniquely decided based on the shape of the scroll, irrespective of the conditions of the pressure during operation. Thus, the pressure in the compression chamber may sometimes be lower than the discharge pressure at the moment when the compression chamber compressed to near the central portion communicates with the discharge port, and hence the fluid may flow back into the compression chamber through the discharge port. This causes pressure loss and energy loss, and further leads to increased variations in the discharge pressure. In other words, pulsation occurs when the fluid flows back into the compression chamber at once from the discharge port, and this causes a noise level increase.
To avoid this, the scroll compressor disclosed in Japanese Unexamined Patent Publication No. H7-189937 closes the discharge port with a check valve made of an elastic body. The check valve is opened/closed at the discharge of a compressed refrigerant to prevent the fluid from flowing back into the compression chamber through the discharge port. In Japanese Unexamined Patent Publication No. H7-189937, one end of the check valve in its longitudinal direction is fixed to the fixed scroll, and the check valve is disposed such that the discharge port provided at the central portion of the fixed scroll is located near a middle portion of the check valve in its longitudinal direction to reduce the impact sound generated at the moment when the check valve is closed.